A Real Puzzler - Low Anti-freeze level in Radiator


#1

I have a condition with low anti-freeze level in the radiator of a 2005 Town & Country that I recently purchased. The level, instead of being up to the bottom of the radiator cap, is 2 1/4" to 2 1/2" below the bottom of the cap when cool. No matter how many times I bring the level back up to full, the level always drops. The level in the overflow tank, while it does go up after the van is driven, always drops back to the same level when cool. I have talked with several other owners of similar vans and all have said that their levels are right up to the bottom of the cap, leading me to believe that I am the odd man out. Here is what I have checked so far.



I put on a new radiator cap. No change. I also put a plastic bag over the cap once and held it in place with a rubber band to make it airtight, just in case it wasn’t sealing completely. Again, no change.

I checked the hose connecting the radiator to the overflow tank and found it to be ok. I also verified that the hose would suction the tank properly and completely, and it does. I even removed the anti-freeze from the tank to be sure the tank was clean and not plugged, and it was fine. I also installed clamps on the end of the hose to be sure the connections were tight. Still no change in the level in the radiator.

I went to a local shop and had them do a cooling system pressure test. It tested OK. They also ran the engine (in my presence) and checked very thoroughly for leaks with the van on a lift. No leaks. And no signs of any leakage at the water pump weep hole. They also burped the system to be sure there was no air (there shouldn’t be since this is the anti-freeze that was in the van when I bought it). Again, no change.

I replaced the upper radiator hose clamps with good quality worm clamps. That also made no difference.



The level in the radiator when cool is always the same as is the level of the overflow tank after it has cooled down. Some of the anti-freeze from the tank is sucked back to the radiator, but not enough to bring the level to full. The amount of anti-freeze required to bring the level up to full is 3 - 4 ounces. I realize this isn’t much, but I would still like to know why this is happening. Does anyone have any other ideas?


#2

Head gasket(s)?

If there are no other leaks in the cooling system, but you still have to add coolant, . . .

Where’s the coolant going?

How can you measure the coolant level as 2 1/4 to 2 1/2 inches below the bottom of the cap? You can’t see that far down into the radiator. What are you measuring?

If you have to keep adding fluid you either have a leak, which you should be able to find, or you have a bad head gasket. There are no other options.


#3

I will also check the hose to the expansion tank. Any cracks in the upper portion of the radiator? Check the oil for any coolant mix.


#4

I had the same problem with a 2000 Blazer last July. The side tank had a small crack (~1") near the top. I had to remove the top of the fan shroud to find the location. Check the side tanks for any leaks dripping down the sides.

Good luck,

Ed B.


#5

So what you are trying to say is that you are completley loosing radiator fluid. It isn’t be diverted from tank to overflow, right?
The only thing it can possibly be is be is either a crack in a water journal or a bad heater core. It shouldn’t be a bad headgasket because you would find some trace of water in your oil. It is very very rare that the headgasket would be the reason why you are loosing fluid and not have any signs of radiator fluid in your oil. You say the mechanic put the van on a lift and looked for leaks - so you know it isn’t a bad expansion plug. But what about the expansion plug that is between the trans and the engine?
I don’t know where the heater core is on your van but I would check that part first. If it ends up that this isn’t the problem, and you have no trace of radiator fluid in the oil, dump the van or rebuild.


#6

There is no loss of coolant. The problem is that the level in the radiator will never stay up to the bottom of the radiator cap. I take fluid from the overflow tank and fill the radiator to full. Then after I drive during the day and check it the next morning cold, the level in the radiator is back down to 2 1/4" to 2 1/2" below the bottom of the cap, while the level in the overflow tank stays constant.
I measure the coolant level with a thin 6" ruler from the top of the fluid to the sealing surface of the bottom of the radiator cap, using a flashlight, of course.


#7

Did you see leakage from the crack? I do not see any leakage and the pressure test was fine.


#8

mharnisch,
edb1961 has a good point: that there may be a crack, or hole, in the radiator side tank. It also, may have a crack in the overflow bottle right at the same level as the radiator level.
Another possibility is the top of the radiator has a partial vacuum air leak. It may seal under water pressure (outward), but, allow air (inward) when a partial vacuum forms during cool-down.


#9

I also verified that the hose would suction the tank properly and completely, and it does.

Red flag. The tank should never be evacuated completely or you’ll be sucking air. It should go no lower than the “cold” line on the side of the overflow container.

I also put a plastic bag over the cap once and held it in place with a rubber band to make it airtight

A plastic bag with a rubber band will never make an airtight seal against the pressure and vacuum of the cooling system.


#10

There is no loss of coolant. The problem is that the radiator is not sucking back in all the coolant that it pushes into the overflow tank. I take fluid from the overflow tank and fill the radiator to full. Then I mark the level of fluid in the overflow tank. After driving for the day, I check the levels the next morning cold. The radiator level has dropped to 2 1/4" to 2 1/2" below the bottom of the cap. The level in the overflow tank is on the mark. Repeating this scenario over a week’s time always has the same results, and I never have to add coolant.
The mechanic did check the oil and it was fine. Since there is no loss of fluid, I think a headgasket leak can be ruled out.


#11

The way I understand it, if there was a leak anywhere in the system below the radiator cap, then under pressure up to 16# I should be able to see a leak. I don’t. Also that should show up in the pressure test. It didn’t. Any leakage above the bottom of the radiator cap would be subjected to less pressure plus vacuum. This would include the top spout of the radiator where the cap fits, as well as the overflow tank and the hose connecting the tank to the radiator spout.
I did verify that the overflow tank was OK by filling it completely full of water and then syphoning through the hose to be sure that at some point there wasn’t a hole where air would be sucked in. The entire tank drained completely.
I agree that at some point the syphoning process is interrupted and air is then sucked in. The most obvious point would be the cap. That is why I covered the cap with a small plastic sandwich bag held tightly to the radiator spout with a rubber band to act as a temporary seal during the cool down process. I thought that if there was not a good vacuum seal at the cap, the bag might make a difference. It didn’t. The only other area that is not under full radiator pressure is the spout of the radiator. I have examined that completely and do not see any problems. Don’t know what to try next.


#12

The reason I syphoned the overflow tank completely was to be sure there wasn’t a problem with the overflow tank or hose. I filled the tank completely with water and syphoned through the hose. The tank emptied completely.
The reason I put a plastic bag over the radiator cap during the cooldown process was a temporary measure to provide an airtight seal just in case the cap was not sealing tightly under vacuum. It made no difference leading me to believe the cap is not the problem.


#13

If I understand you correctly, a bag OVER the cap with a rubber band to secure it to the neck is not “airtight” especially against the vacuum being pulled over a fairly long time period.

Now I understand your statement about completely emptying the overflow. Any air in the system will end up at the highest point. That isn’t the rad neck by any chance, is it? Assuming you fill the rad to overflowing, put the cap on, fill the overflow tank, then cycle the coolant a few times through hot/cold cycles and air still appears at the cap, perhaps you have a slight leak elsewhere in the system or a small combustion chamber leak. It ends up at the cap. Depends on system design…


#14

i had an interestingly similar issue with my old '90 caravan.

the radiator was a generic type for chrysler that year. the top of the radiator cap had three small (1/8" or so) brazed in to the neck, just under the rad cap.

only one was used (to take overflow to overflow tank) the other two were capped off with small rubber caps. eventually one if them dry rotted and sprung a leak. it would only leak when the rad cap was venting, not during cool down or warm up.

i couldn’t find it until i pulled over on the interstate, and immediately opened the hood and there it was, spewing a tiny jet of antifreeze.

may not be your issue, but look anyway. good luck


#15

I put the bag over the cap only one time just after having driven the van but before the cool down cycle started. I thought that it might help better seal against an air leak should the cap not be sealing tightly. This didn’t make any difference. I would think the bag would have had some effect if there was a leak at the cap. Anyway, there is never any coolant around the cap that would indicate the cap is not sealing tight.
The neck of the radiator is the highest point in the system. If there were a leak, then I would have to be adding anti-freeze to maintain a certain level, but I do not. If I fill the radiator to full, mark the level in the overflow tank, then go through a heating/cooling cycle, the level in the radiator will be 2 1/4" to 2 1/2" below the bottom of the cap and the level in the overflow tank will be on the mark. If I go through another heating/cooling cycle, the levels will be the same. Another heating/cooling cycle, the same results. No loss of coolant so no need to add any.


#16

Mine only has one outlet that is connected to the hose that goes to the overflow tank. I understand how you would have trouble finding your leak. When the radiator cap is venting, it is not under the full system pressure, but somewhat less. The pressure does not build up because it has an outlet to go to the overflow tank. This would only occur when the cap vented, as you mentioned. However, thanks for the suggestion.


#17

“No matter how many times I bring the level back up to full, the level always drops.”

I read this in the original post and assumed the OP had been adding coolant all along. If the OP has not had to any coolant then I’m not sure what the statement means.

I just remembered, I would sometimes catch a whiff of antifreeze for a week or two before I found the leak in the Blazer. First, I thought the intake gasket was leaking, I was almost relieved when I found out it was the radiator.

I could see a little coolant leaking out of the crack when the engine was hot, but it took a while to find it. A flashiight helps since it reflects off any moisture present.

Ed B.


#18

You don’t have to add fluid AND it doesn’t overheat? Don’t worry, be happy!


#19

isn’t there a note, sign or a paragraph on this; in, on or around the engine compartment? or in the manual? i could have sworn mine has a note that ‘full is X .X" below the neck.’

and isn;t the neck actually a tube which extends down into the top of the rad? thus the couple inch column?


#20

Anyway, there is never any coolant around the cap that would indicate the cap is not sealing tight.

The cap seals against both pressure and vacuum. There is a spring loaded seal. It can leak during either phase. So it’s not necessarily indicative if there is no coolant leaking past it.

If there were a leak, then I would have to be adding anti-freeze to maintain a certain level.

Leaks do not always work both ways. You can have a vacuum leak that does not produce visible coolant loss on positive pressure. Then there’s the possibility of a slight combustion chamber leak too.